1. Field of the Invention
The present invention relates to a radiation-sensitive resin composition suitable as a chemically-amplified resist useful for microfabrication utilizing various types of radiation, for example, ultraviolet rays such as g-line or i-line, (extreme) deep ultraviolet rays such as a KrF excimer laser, ArF excimer laser, F2 excimer laser, or EUV, X-rays such as synchrotron radiation, and charged particle rays such as electron beams.
2. Description of Background Art
In the field of microfabrication represented by the manufacture of integrated circuit devices, lithographic technology enabling microfabrication with a line width of 0.20 μm or less has been demanded in order to increase the degree of integration in recent years.
A conventional lithographic process utilizes near ultraviolet rays such as i-line radiation. It is known in the art that microfabrication with a line width of a sub-quarter micron order using near ultraviolet rays is very difficult.
Therefore, use of radiation with a shorter wavelength has been studied to enable microfabrication with a line width of 0.25 μm or less. As radiation with a shorter wavelength, deep ultraviolet rays represented by a line spectrum of a mercury lamp and an excimer laser, X-rays, electron beams, and the like can be given. Of these, a KrF excimer laser (wavelength: 248 nm), an ArF excimer laser (wavelength: 193 nm), an F2 excimer laser (wavelength: 157 nm), EUV (wavelength 13 nm), and electron beams have attracted attention.
As a radiation sensitive resin composition applicable to short wavelength radiations, a number of compositions utilizing a chemical amplification effect between a component having an acid-dissociable functional group and a photoacid generator which generates an acid upon irradiation (hereinafter called “exposure”) has been proposed. Such a composition is hereinafter called a chemically-amplified radiation sensitive composition.
As the chemically-amplified radiation-sensitive composition, a composition comprising a polymer containing a t-butyl ester group of carboxylic acid or a t-butylcarbonate group of phenol and a photoacid generator has been proposed. This composition utilizes the effect of the polymer to release a t-butyl ester group or t-butyl carbonate group by the action of an acid generated upon exposure to form an acidic group such as a carboxylic group or a phenolic hydroxyl group, which renders an exposed area on a resist film readily soluble in an alkaline developer. A problem with this type of radiation-sensitive resin composition has been diffusion of an acid produced by exposure to radiation in the unexposed area, making it difficult to obtain a resist with high resolution. To overcome this problem, use of a basic compound such as an amine has been proposed (e.g. Japanese Patent Applications Laid-open No. 127369/1993, 266111/1994, and 146558/1995).
As acid generators used in the photolithographic process that has become more and more micronized in recent years, iodonium salts, sulfonamides, oxime sulfonates, and the like have attracted special attention due to the higher transparency to various radiations than conventional triarylsulfonium salts, in addition to alkyl sulfonium salts with higher activity. Although many of these acid generators have advantages over triarylsulfonium salts in terms of high resolution and the like, these acid generators are unstable in bases in general. If a trialkylamine, unsubstituted imidazole, and the like that have conventionally been used as acid diffusion inhibitors are added, storage stability as a resist composition is impaired due to their action of nucleophilically decomposing the acid generator in the resist composition. However, conventional acid diffusion inhibitors with weak basicity cannot exhibit a sufficient acid diffusion inhibiting effect, are liable to be affected by basic substances in the environment, and exhibit only poor environmental resistance.
An object of the present invention is to provide a radiation-sensitive resin composition useful as a chemically amplified resist exhibiting high resolution and high storage stability, and sensible to active radiations, for example, ultraviolet rays such as g-lines and i-lines, deep ultraviolet rays represented by a KrF excimer laser, ArF excimer laser, F2 excimer laser, and EUV excimer laser, and electron beams.
As a result of extensive studies, the present inventors have found that a later described specific compound and a composition comprising this compound can achieve this object.